MINERAL AND SOIL RESOURCES

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CHAPTER 13

• MINERAL AND SOIL RESOURCES

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Great Terrain Robbery

• What are the provisions of the 1872 law?
• How much U.S. land has become private property as
  a result of this law?
• Land has been leased by private individuals over
  and over
• Land has been mined and abandoned
• No provisions for reclamation of damaged land
  exists ! What a fraud!

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Geologic Processes What is Earths structure

• Core - solid interior, surrounded by molten
  material
• Mantle - thick, solid zone surrounding core -
  most solid but athenosphere is plastic-like
• Crust - thinnest consists of continental crust
  and oceanic crust - 71

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Plate tectonics - internal geologic processes

• Outermost part of mantle and crust is
  lithosphere plates move over surface of
  athenosphere
• plate tectonics is theory explaining movements of
  plates and processes, like volcanoes, that occur
  at their boundaries
• continental drift - portions of continental crust
  (plates) moved apart

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Plate tectonics - internal geologic processes -2

• Separated continents isolated populations --gt
  reproductive isolation --gtspeciation
• Boundaries of lithosphere plates
• divergent plate boundaries - plates move apart in
  opposite directions --gt trenches
• convergent plate boundaries - plates pushed
  together --gt mountains oceanic ridges
• subduction zone - one plate slides under other
• transform fault - plates move opposite but
  parallel along fracture --gt earthquakes

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Geologic processes on Earths surface

• External processes dependent on sun and gravity -
  tend to wear down surface
• Erosion- material is dissolved, loosened or worn
  away
• Water carries material to sea --gt deltas cutting
  valleys on the way
• Wind carries sand
• Erosion accelerated by Mans activities

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Mineral Resources the rock cycle

• Mineral - element or inorganic compound solid -
  often crystalline - occurs naturally
• Rock - more general term for crust material
• igneous - molten rock (magma) emerges to surface
  and hardens
• sedimentary - eroded bits settle in surface water
  layers, are buried and compacted
• metamorphic - high temps and pressure act on
  preexisting rock --gt change
• Rock cycle - rocks change type

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What are mineral resources?

• Rock cycle very slow - resources produced
  considered nonrenewable
• Mineral resources include
• energy resources - coal uranium
• metallic mineral resources - iron copper
• nonmetallic mineral resources - salt clay
• ore - metal yielding material that can be
  economically extracted

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What are mineral resources?-2

• Mineral resources may be
• identified resources
• reserves if they can be extracted economically
• potential reserves - may become reserves
• undiscovered resources
• exploration may make these potential reserves

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Finding removing mineral deposits

• Subsurface mining -underground mines are
  expensive and dangerous but less damaging
• Surface mining - strips away overburden (spoil)
• strip mining (fig. 13.8) and dredging
• area strip mining - spoils fill trenches as new
  trenches are dug --gt spoil banks (fig. 13.9)
• contour strip mining - hilly or mountainous
  terrain --gt easily erodable highwall (fig. 13-10)
  of spoil - used for coal mining in Appalachia

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Estimating supplies of nonrenewable mineral
resources

• Quantity actually or potentially available
• Rate at which supply is used
• Economic depletion - resources exist, but cost of
  mining, etc., is greater than returns
• For reserves, what is depletion time?
• Reserve-to-production ratio - of years reserve
  will last at current production rates
• depletion curves depend on recycling, reuse,
  new discoveries see U.S. mineral use (p. 334)

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Increasing mineral resource supplies

• Economics determines what part of known supply is
  used
• Price is determined by supply as supply
  diminishes cost rises --gtbetter mining technology
• Depletion allowances subsidize domestic mineral
  resource development
• benefit of national security or economy
• encourage environmental destruction
• discourage recycling

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Increasing mineral resource supplies

• Why not tax extraction of non-fuel mineral
  resources? This would
• provide revenue to government
• provide efficient resource use incentive
• promote waste reduction and pollution prevention
• encourage recycling and reuse

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Finding new deposits

• Geologic exploration will increase current
  reserves especially in unexplored areas
• But only 1 in10,000 possible deposits will
  become a producing mine or well
• Use lower grade ores?
• mining becomes prohibitively expensive
• fresh water becoming limiting factor
• waste material adversely impacts environment

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Finding new deposits - 2

• What about mining the ocean? - in seawater and on
  continental shelf and deep-ocean floor
• concentrations low in seawater
• continental shelf is already mined
• deep ocean floor - nodules of ore could be sucked
  up or vacuumed up
• Problems - who owns sea bed? What will be effect
  of dumping byproducts? Will it seriously endanger
  unknown marine diversity?

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Finding substitutes for scarce nonrenewables

• The materials revolution
• As metals become expensive or scarce, they are
  being replaced by silicon, ceramics and plastics
• Problems
• phasing in a substitute is time consuming and
  costly
• finding substitutes for some resources is
  impossible
• some substitutes are inferior

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Environmental effects of extracting and using
mineral resources

• Scarring and disruption of land surface
• Underground coal mine fires unquenchable
• Subsidence of land over underground mines
• Wind or water-caused erosion of spoils and
  tailings
• Acid mine drainage - contamination of streams and
  groundwater--gtaquatic life loss

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Environmental effects of extracting and using
mineral resources - 2

• What are components of ore?
• ore mineral- the desired metal
• gangue - waste mineral material
• tailings - waste following benefaction (mill
  separation)
• Smelting process produces pollutants which kill
  nearby vegetation and cause water pollution
• Grade of ore ( mineral content) determines
  environmental impact of mining it effect on
  environment increases over time

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Should 1872 Mining law be reformed?

• Should land be leased, with impact assessments
  strict environmental restrictions, rather than
  sold?
• Should mining companies be legally re-sponsible
  for damage, post environmental performance bonds,
  pay rents, pay royalties.
• Mining companies say they will be forced to mine
  in other counties --gt America loss of jobs

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Soil The Base of Life

• Soil is potentially renewable - but very slowly
  made by weathering, sediment deposit, and
  decomposition of organic matter
• Soil profile shows zones (soil horizons)
• surface-litter layer (O horizon)
• topsoil layer (A horizon) humus inorganic
• subsoil (B horizon) inorganic mixture
• bedrock (C horizon) unweathered parent rock

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Soil the base of life - 2

• Soil pore contain air and water - both needed by
  plant roots
• Precipitation first infiltrates downward and
  dissolves soil components and carries them
  downward (leaching)
• Soil maturation is slow
• Mature soil varies in color, content, pore space,
  acidity and depth 5 soil types

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Texture, porocity, acidity differences

• Texture - depends on types and sizes of mineral
  particles from clay-silt-sand-gravel
• somewhat equal amounts of each --gt loam
• Porosity - volume of pores or spaces for air and
  water determines soil permeability
• Acidity(low pH - lime may be added) versus
  alkalinity (high pH-sulfur may be added) -
  determines uptake of soil nutrients

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Soil Erosion

• Movement of soil components mostly by air and
  water.
• Roots of vegetated ecosystems oppose erosion by
  anchoring soil
• Farming, logging, off-road vehicles,
  construction, overgrazing, and burning destroy
  plant cover --gt increased erosion
• The nation that destroys its soil destroys
  itself said by ..

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Types of erosion

• Water erosion
• sheet erosion - topsoil removed evenly by water
• rill erosion - water cuts channels in soil
• gully erosion - channels join --gtwider deeper
• Fertility declines with erosion sediment
  pollutes reservoirs
• Annual erosion rates are 7-100x natural renewal
  rate (16 in U.S.)

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Global soil erosion problem

• 15 of land too eroded to grow crops, due to
• overgrazing (35)
• deforestation (30)
• unsustainable farming (28)
• Population to feed increases arable topsoil
  decreases (7/decade) - reduction in crop
  productivity, need for fertilizers (not really a
  good substitute

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Desertification problem

• Definition Productive potential of arid or
  semiarid lands falls by 10 or more
• moderate - 10 - 25 drop in productivity
• severe - 25 - 50 drop in productivity
• very severe - 50 or more drop in productivity
• Five major causes.(expense to rectify)
• Four major consequences.
• 40 of world experiencing desertification

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Soil degradation by excess salt and water

• Irrigation increases crop yields, but water
  carries salts, etc, that remain in soil after
  evaporation --gt salinization (20 -30)
• Salts can be flushed out, but very expensive
• waterlogging - irrigation --gt raising water
  table saline water envelops and kills roots

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Solutions Soil conservation

• Definition - reducing soil erosion and restore
  soil fertility
• Conventional-tillage farming - fall plowing after
  harvest preparation for spring planting
• Conservation-tillage farming disturb soil less
• minimum tillage farming - loosen but do not turn
  over soil
• no-till farming - seeds, fertilizers and
  weed-killers added to unplowed soil

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Solutions Soil conservation -2

• Conservation tillage reduces soil erosion it
  also saves fuel, cuts costs, soil hold water,
  becomes less packed, multiple cropping
• Herbicide need - not necessarily increased
• Now used on about 40 U.S. cropland

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Terracing, contour farming

• Sloped farmland is terraced run across land
  contour initial work in forming terraces
• Contour farming - plant rows follow land contours
  - each acts as small dam
• Strip cropping - alternate rows of different
  crops --gt covering soil --gt reduce erosion
• Alley cropping (agroforestry) - crops planted
  between strips of hardwood (trees)

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Gully reclamation

• Quick growing plants, shrubs, vines, and trees
  planted in bare soil
• Windbreaks - rows of trees protect land from wind
• Land classification - what should not be planted
• PAM - particles bind to soil --gt soil cohesiveness

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Maintenance and restoration

• Organic fertilizers
• animal manure use has declined - separation of
  animals and croplands
• green manure- plow vegetation into soil
• compost - from alternating layers of
  nitrogen-rich wastes
• Crop rotation - alternate planting of legumes and
  nutrient-depleting crops

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Maintenance and Restoration -2

• Inorganic fertilizers contain nitrogen,
  phosphorus and potassium
• Useful because easily transported, stored and
  applied
• Use increased 50s to 89 declined since
• Problems do not add humus porosity declines
  all needed nutrients not added
• Eutrophication - fertilizer runoff